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Recent studies have shown reduced breath hydrogen (H2) excretion in methane (CH4)-producing healthy individuals following ingestion of lactulose. This questions the reliability of the breath hydrogen test (BHT) in CH4 excretors, but the relationship between CH4 and H2 excretion in other clinical applications of the BHT is not known. We reviewed BHT results in two groups of subjects: (1) 385 children tested for lactose malabsorption in a hospital setting, and (2) 109 lactose-malabsorbing patients tested with a home kit. The percentage of lactose malabsorbers in group 1 (51%) was the same regardless of CH4-producing status (P = 0.97). The BHT data from group 2 showed a positive correlation (r = 0.6, P < 0.000001) between the magnitude of the rise in CH4 and H2 concentrations, and the H2 excretion curves were significantly higher in the CH4-producing individuals. We conclude that attention to CH4-producing status is not necessary in the interpretation of the lactose BHT.

Breath hydrogen testing (BHT) is a simple and reliable method for identifying impaired carbohydrate absorption. We describe a laboratory exercise in physiology for medical students using BHT as the teaching tool. The students collect fasting samples of expired air from each other using a simple nasal prong technique. They then drink one of several different aqueous carbohydrate solutions. Additional samples of expired air are collected by the students at 90 and 120 min after substrate ingestion and are analyzed by gas chromatography. Between sampling periods, discussions of digestive physiology are provided by the faculty. Students tabulate their BHT results as well as recording any symptoms using a standard scoring system. A total of 460 students have participated. We found that the percentage of students who malabsorbed a given substrate was similar each year. The results obtained in these student exercises closely parallel those reported in the literature. We conclude that BHT is an excellent teaching tool for illustrating carbohydrate digestion and absorption, even when performed by minimally trained subjects.